Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare destructiveHint=true, idempotentHint=false, and readOnlyHint=false, so the safety profile is covered. The description adds genuinely new behavioral context: the fallback only ever targets this connection's own running session and never another session's, which bounds the blast radius in a way the annotations do not.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two sentences, zero padding, and the primary action is front-loaded ahead of the parameter guidance. Every clause carries operational information.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a two-parameter destructive tool whose annotations carry the safety profile and whose schema documents both params, the description covers the remaining gaps: deletion scope, parameter sourcing, and default target. No output schema exists, so return values need not be explained.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the baseline is 3; the description exceeds it by explaining where session_id comes from and what happens when it is absent. The op_id semantics are fully handled in the schema itself, so no further description is needed.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource (delete a session) plus an explicit scope: running or finished. The phrase "so it no longer counts" separates it from the adjacent stop_session/edit_session siblings, which imply halting or modifying rather than removing.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives concrete guidance: pass session_id sourced from get_now or list_sessions, and states the default behavior when it is omitted (only this connection's single running session). It does not explicitly contrast with stop_session when a running session should be halted instead of deleted, so usage context is clear but not complete.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.